On the Validity of Radiocarbon Dates from Snail Shells

Abstract

The use of snail shells for dating Pleistocene events by the $C^{14}$ method has been questioned. If snails in some manner incorporate into their shells the $C^{14}$-free carbonate of the limestone in their environment, $C^{14}$ dates derived from these diluted shells would appear too old. The uptake of inorganic carbon in snail shell matter was measured by feeding $C^{14}$-labeled $CaCO_{3}$ to aquatic and terrestrial snails. The activity of the new shell growth indicates that 10-12 per cent uptake is possible, yielding an uncertainty in the $C^{14}$ date of approximately one thousand years.